With the recent increase in concern about environmental issues, the demand on automobiles for better fuel economy is increasing. Better fuel economy is also being required of rubber compositions used for automotive tires. For example, rubber compositions containing a conjugated diene polymer (e.g. polybutadiene, butadiene-styrene copolymer) and a filler (e.g. carbon black, silica) are used for automotive tires.
The addition of a polymer having a low glass transition temperature, such as polybutadiene rubber, is known as a technique for improving fuel economy. The addition of polybutadiene rubber improves fuel economy but tends to deteriorate wet-grip performance. On the other hand, no addition of polybutadiene rubber tends to deteriorate abrasion resistance. Thus, methods for achieving a balanced improvement in fuel economy, wet-grip performance, and abrasion resistance are demanded.
Moreover, automotive tires need to have handling stability to ensure safety. Thus, improvements in handling stability as well as fuel economy, wet-grip performance, and abrasion resistance are demanded.
Patent Literature 1 proposes a method of improving fuel economy by using a diene rubber (modified rubber) that is modified by an organosilicon compound containing an amino group and an alkoxy group. Unfortunately, this method still has room for improvement in terms of achieving a balanced improvement in fuel economy, wet-grip performance, abrasion resistance, and handling stability.